The present invention relates to a positioning servo controller (position control apparatus) which performs positioning of a controlled object, and more particularly a positioning servo controller for positioning a motor.
FIG. 30 is a control block diagram showing the configuration of a conventional positioning servo controller. As shown in FIG. 30, the conventional positioning servo controller is configured by a position controller 1, a speed controller 2, a torque amplifier 3, a motor 4, and a differentiator 5.
The positioning servo controller controls the position xcex8 [rad] of the motor 4 in which the inertia is J [Nxc2x7mxc2x7s2].
The motor 4 is provided with an encoder (not shown), so that the position xcex8 of the motor 4 can be detected by the encoder. A position deviation (xcex8r-xcex8) between a position command xcex8r which is supplied from a higher-level unit (not shown), and the position xcex8 of the motor 4 is input to the position controller 1.
The position controller 1 is a proportional controller which outputs a value obtained by multiplying the deviation with a position loop gain Kp [1/s], as a speed command xcfx89r [rad/s] for the motor 4.
The differentiator 5 differentiates the position xcex8 [rad] of the motor 4, and outputs the speed xcfx89 [rad/s] of the motor 4.
The speed controller 2 is a proportional controller which receives a speed deviation between the speed command xcfx89r [rad/s] and the speed xcfx89 [rad/s] of the motor 4, and which outputs a value obtained by multiplying the deviation with a speed loop gain Kv [Nxc2x7mxc2x7s], as a torque command Tref [Nxc2x7m] for the motor 4.
The torque amplifier 3 receives the torque command Tref, and generates a torque Tr to drive the motor 4.
Namely, the positioning servo controller is used for causing the position xcex8 of the motor 4 to follow the position command xcex8r. The position xcex8 of the motor 4 is a position response with respect to the position command xcex8r.
In such a conventional positioning servo controller, the feedback control system in which a positioning control is conducted on the basis of the fed-back position response xcex8 of the motor 4 is used.
As described above, usually, the positioning servo controller has the speed loop process as a minor loop, in the position loop process.
In such a positioning servo controller of the feedback control system, however, the values of the position loop gain Kp and the speed loop gain Kv are finite values and have the upper limit.
Therefore, the position response xcex8 of the motor 4 fails to completely coincide with the position command xcex8r, and so-called servo delay occurs.
FIGS. 31(a) and 31(b) are the graphes showing the operation of the conventional positioning servo controller.
In FIG. 31(a), the position command xcex8r and the position response xcex8 are shown, and, in FIG. 31(b), differentials dxcex8r/dt and dxcex8/dt of the position command xcex8r and the position response xcex8 are shown.
As shown in FIGS. 31(a) and (b), dxcex8r/dt is a command of accelerating the motor 4 at a constant acceleration, and, after the motor reaches a steady-state speed V [rad/s] and movement at the steady-state speed V is conducted for a predetermined time period, decelerating the motor at a constant acceleration.
In this case, the position deviation is V/Kp [rad] at the maximum, and the time period between a timing when the value of dxcex8r/dt becomes 0 and that when the position response xcex8 actually reaches the value of the position command xcex8r is prolonged in proportion to 1/Kp [s].
FIGS. 31(a) and 31(b) show manners of variations of the commands xcex8r and dxcex8r/dt and the responses xcex8 and dxcex8/dt in the case where the acceleration/deceleration time=0.1 [s], the steady-state speed V=100 [rad/s], the predetermined time period=0.2 [s], the position loop gain Kp=25 [1/s], the speed loop gain Kv=200 [Nxc2x7mxc2x7s], and the inertia J=1 [Nxc2x7mxc2x7s2].
In FIGS. 31(a) and 31(b), the steady-state deviation is V/Kp=100/25=4 [rad], and the time period between a timing when dxcex8r/dt becomes 0 and that when the value of the position response xcex8 actually reaches that of the position command xcex8r is 0.1 [s].
In such a positioning servo controller, in order to eliminate the above-mentioned servo delay, the feedforward control system is sometimes used together with the feedback control system.
FIG. 32 is a control block diagram showing the configuration of a positioning servo controller in which the feedforward control system is used together with the feedback control system.
The positioning servo controller comprises feedforward controllers 6 and 7 in addition to the components of the positioning servo controller of FIG. 2.
The feedforward controller 6 receives the position command xcex8r, differentiates the position command xcex8r, and outputs a value which is obtained by multiplying the differential value with a first feedforward gain Kff1 [1/s].
The value is a first feedforward controlled variable which is to be added to the speed command xcfx89r [1/s] that is output from the position controller 1.
According to the configuration, in the positioning servo controller of FIG. 32, the speed loop process is conducted on the basis of the speed command which is directly produced from the position command xcex8r, and which does not contain a servo delay element. Therefore, the servo delay can be further eliminated as compared with the case where only the feedback control is used.
The feedforward controller 7 receives a first feedforward compensation amount output from the feedforward controller 6, differentiates the compensation amount, and outputs a value which is obtained by multiplying the differentiation with a second feedforward gain Kff2, as a second feedforward compensation amount.
The second feedforward compensation amount is added to the value output from the speed controller 2, and the result of the addition is input as the torque command Tr to the torque amplifier 3.
According to the configuration, the torque amplifier 3 can drive the motor 4 on the basis of the torque command Tr which does not contain a servo delay element.
As described above, in the positioning servo controller of FIG. 32, servo delay which may be generated by the feedback control can be compensated by conducting the speed feedforward control and the torque feedforward control.
FIG. 33 is a control block diagram showing the blocks of the positioning servo controller of FIG. 32 in a simplified manner. As shown in FIG. 33, the control performance of the positioning servo controller depends on the values of the feedforward gains Kff1 and Kff2.
In the positioning servo controller of FIG. 32, therefore, the motor 4 is controlled in a state where the feedforward gains Kff1 and Kff2 are set to optimum values so that servo delay is reduced to a degree as small as possible.
When the feedforward gain Kff1=1, the control block diagram of the positioning servo controller is as shown in FIG. 34.
When the feedforward gain Kff2=J, the transfer function G from the position command xcex8r to the position response xcex8 has a value of 1, and ideally no delay occurs between the position command xcex8r and the position response xcex8, so that servo delay of the positioning servo controller is 0.
In practice, however, it is often that physical quantities such as the inertia J of the motor 4 which is the controlled object are not completely grasped, and it is difficult to set the values of the feedforward gains Kff1 and Kff2 to optimum values.
In such a case, during a process of positioning the motor 4, a phenomenon such as an overshoot or an undershoot occurs. When Kff2=J, for example, servo delay of the positioning servo controller is 0. In the case where the value of J is unknown, however, the value of the feedforward gain Kff2 cannot be set to that of J, and hence an overshoot or an undershoot occurs in the response.
FIGS. 35(a) and 35(b) show manners of variations of the speed response dxcex8/dt which is a differential of the position response xcex8 of the positioning servo controller in the case where the value of the feedforward gain Kff2 is not optimumly set.
In FIGS. 35(a) and 35(b), Kff2=0.5=J/2.
FIG. 35(b) is an enlarged view of the portion A in FIG. 35(a).
As shown in FIG. 35(b), an overshoot occurs in the speed response dxcex8/dt.
In order to eliminate such an overshoot, a countermeasure such as that the value of the feedforward gain Kff1 is reduced, or that a filter is disposed in the output of the feedforward controller 7 has been taken. However, the conventional positioning servo controller has a problem in that servo delay is again produced by such a countermeasure.
Returning to FIG. 30, the conventional positioning servo controller is configured by the position controller 1, the speed controller 2, the torque amplifier 3, the motor 4, and the differentiator 5. The conventional positioning servo controller controls the position xcex8 [rad] of the motor 4 in which the inertia is J [Nxc2x7mxc2x7s2].
For the sake of simplicity of description, it is assumed that the controlled object is a rigid body and the total inertia of the controlled object and the motor 4 is J, and also that the response of the torque amplifier 3 is so fast as to be negligible.
As described above, in the positioning servo controller, usually, a speed loop having the speed loop gain Kv is disposed as a minor loop in the position loop process. The torque amplifier 3 which generates a torque is disposed in the speed loop. The motor of the inertia J is rotated by the generated torque Tr. The position xcex8 is read into the controller by the encoder to be used in the control. In such a conventional positioning servo controller, a machine is coupled to the end of the motor, and it is important to adjust the values of Kp and Kv in a well-balanced manner in accordance with the characteristics of the machine and the operation requirement use.
As shown in FIG. 36, the response characteristic in the case where a step command is input to the control system of FIG. 30 is variously changed depending on the combination of the values of Kp and Kv.
In FIG. 36, three kinds of lines, or lines (a) to (c) are drawn. The lines respectively show response characteristics in the following manner:
(1) (a) shows the case where Kv=50 and Kp=10,
(2) (b) shows the case where Kv=100 and Kp=25, and
(3) (c) shows the case where Kv=50 and Kp=50.
It is assumed that J=1 in all the cases.
For example, the case will be considered in which the requested specification is that, as shown in the line (b) of FIG. 36, an overshoot does not occur and a high response is attained, and the initial state is the state of the line (a) of FIG. 36. When adjustment is to be conducted in accordance with the request, the value of Kp is first gradually increased while monitoring the waveform of the position feedback, and, when the state of the line (c) of FIG. 36 is attained, the value of Kv is then gradually increased. As a result, the state of the line (b) of FIG. 36 is obtained.
In a usual case, when Kv is excessively increased, however, the servo system oscillates because of the mechanical system which is neglected in the above, and delay of the torque amplifier 3 disposed in the speed loop.
When oscillation occurs during the course of increasing Kv, therefore, the value of Kp must be again reduced, and an optimum value of Kv must be then searched.
As described above, in the conventional positioning servo controller, it is required to adjust an optimum gain while alternatingly changing the values of Kp and Kv. Unless the relationship between Kp and Kv is fully known, it is difficult to perform the adjustment in a well-balanced manner.
Specifically, a skilled person knows that the controlled object in the configuration of FIG. 6 is a rigid body, and, when the total load inertia of the motor and the machine is J, the state of the line (b) of FIG. 36 can be obtained by setting Kv=4xc2x7Kpxc2x7J. However, it is difficult for a person who has little experience and knowledge to achieve the balance.
FIG. 37 is a control block diagram showing another conventional positioning servo controller which is slightly different in configuration from the conventional positioning servo controller of FIG. 30. As shown in FIG. 37, the conventional positioning servo controller is configured by a position controller 1, a speed controller 2, a motor 4, and a differentiator 5.
The conventional positioning servo controller controls the position xcex8 [rad] of the motor 4 in which the inertia is J [Nxc2x7mxc2x7s2].
Usually, a torque amplifier which receives a produced torque command and generates a torque to drive the motor 4 is disposed. However, it is assumed that the response of the torque amplifier is so fast as to be negligible, and hence the torque amplifier is not shown in the figure.
For the sake of simplicity of description, it is assumed that the controlled object is a rigid body and the total inertia of the controlled object and the motor 4 is J.
The motor 4 is provided with an encoder (not shown), so that the position xcex8 of the motor 4 can be detected by the encoder. A position deviation between a position command xcex8r which is supplied from a host apparatus (not shown), and the position xcex8 of the motor 4 is input to the position controller 1 and the differentiator 5.
The position controller 1 is a proportional controller which outputs a value obtained by multiplying the deviation with a proportional gain Kp [Nxc2x7mxc2x7s2].
The differentiator 5 outputs a value which is obtained by differentiating the position deviation between the position command xcex8r and the position xcex8 of the motor 4.
The speed controller 2 is a proportional controller which outputs a value obtained by multiplying the value obtained by the differentiator 5, with a differential gain Kd [1/s] The conventional positioning servo controller is used for causing the position xcex8 of the motor 4 to follow the position command xcex8r. The position xcex8 of the motor 4 is a position response with respect to the position command xcex8r.
The torque for controlling the motor 4 in the conventional positioning servo controller is produced by the torque amplifier which is not shown, by using as the torque command a value obtained by adding together the values output from the position controller 1 and the speed controller 2.
FIG. 38 shows another conventional positioning servo controller which further comprises an integrator 6 and an integration controller 3 in addition to the conventional positioning servo controller shown in FIG. 37.
The integrator 6 integrates the position deviation between the position command xcex8r and the position of the motor 4, and outputs the value of the integration. The integration controller 3 amplifies the value obtained by the integrator 3 by an integral gain Ki, and outputs the amplified value.
The torque for controlling the motor 4 in the conventional positioning servo controller is produced by the torque amplifier which is not shown, by using as the torque command a value obtained by adding together the values output from the position controller 1, the speed controller 2, and the integration controller 3.
In the conventional positioning servo controllers shown in FIGS. 37 and 38, in order to enable the response of xcex8 with respect to the position command xcex8r, that of xcex8 with respect to a disturbance Td, and the like to exert a desired performance, it is necessary to adjust the values of the gains Kp, Kd, and Ki to optimum values.
In the case where the controlled object (the total of the actuator and the machine coupled to the actuator) is an ideal rigid body, the adjustment can be easily obtained according to a control theory. In an actual controlled object, however, friction and spring elements exist, and hence the adjustment is usually conducted by cut and try.
Therefore, the parameter adjustment is a cumbersome work.
FIGS. 39 and 40 show conventional positioning servo controllers for solving the problem.
In FIG. 39, amplifiers 27 and 28 are added to the conventional positioning servo controller shown in FIG. 37, and, in FIG. 40, amplifiers 27, 28, and 29 are added to the conventional positioning servo controller shown in FIG. 38.
The amplifier 27 amplifies the value output from the position controller 1 by a value Kg2 which is obtained by squaring an adjustment gain Kg, and outputs the amplified value.
The amplifier 28 amplifies the value output from the speed controller 8 by the adjustment gain Kg, and outputs the amplified value.
The amplifier 29 amplifies the value output from the integration controller 3 by a value Kg3 which is obtained by cubing the adjustment gain Kg, and outputs the amplified value.
In the conventional positioning servo controller, the parameter Kg for simultaneously changing a proportional element, a differential element, and an integral element is introduced, and, when the proportional gain Kp, the differential gain Kd, and the integral gain Ki are once determined, the gain adjustment can be conducted while achieving the balance, simply by changing the adjustment gain Kg which is one parameter. Therefore, it is possible to easily realize a requested response characteristic.
In the conventional positioning servo controllers shown in FIGS. 39 and 40, however, there arises a problem in the case where the disturbance response is taken into consideration.
In the conventional positioning servo controller shown in FIG. 40, for example, the command response which is a response of a position deviation xcex81 with respect to the position command xcex8r, and the disturbance response which is a response of a position deviation xcex82 with respect to the disturbance Td are calculated as shown in FIG. 41.
In this control system, even when Kp, Kd, Ki, and Kg are adjusted so as to reduce the position deviation xcex82 caused by the influence of the disturbance Td, also the position deviation xcex81 in the command response is changed together with the position deviation xcex82 in the disturbance response because also the transfer function from the position command xcex8r to the position deviation xcex81 depends on only the same parameters.
Namely, such a configuration is a so-called one-degree of freedom control system, and hence the adjustment cannot be adequately conducted by using only the adjustment gain Kg on the feedback side.
As a method of eliminating servo delay, there is a method in which, as in a positioning servo controller which is shown in FIG. 1 and described later, a speed feedforward controller 6, an acceleration feedforward controller 7, and an acceleration controller 8 that performs an acceleration feedback control on the basis of the deviation between the acceleration of the motor 4 and an acceleration command to output the torque command to the torque amplifier 3 are added.
On the other hand, as a method in which optimum adjustment of the positioning state of the position response xcex8 is easily conducted by adjusting various parameters of the control system such as the position loop gain Kp and the speed loop gain Kv, there is a method in which, as in a positioning servo controller which is shown in FIG. 5 and described later, an amplifier 10 that multiplies an input with the adjustment gain Kg is disposed behind the position controller 1 and the speed controller 2.
In such a positioning servo controller, however, the adjustment gain and the feedforward gain are adjusted by try and error to conduct optimum adjustment of the positioning state, and hence there is a problem in that the adjustment requires a prolonged time period.
As described above, in the conventional positioning servo controller shown in FIG. 30, when physical quantities of the motor which affect the control are unknown, the values of control parameters such as a feedforward gain cannot be set to optimum values, thereby producing a problem in that an overshoot or an undershoot occurs in a control response and a satisfactory control response cannot be obtained.
It is a first object of the invention to provide a positioning servo controller in which, even when physical quantities of a motor are unknown, a satisfactory control response can be obtained.
In the conventional positioning servo controller described above, the two parameters must be adjusted, and hence there is a problem in that it is difficult to easily realize a requested response characteristic.
It is a second object of the invention to provide a positioning servo controller in which a requested response characteristic can be easily realized.
The conventional positioning servo controller of FIG. 37 described above has a problem in that, even when the adjustment gain is used in order to adjust the gain of the feedback control system by one parameter, it is difficult to easily realize a requested response characteristic in the case of adjustment of the disturbance response.
It is a third object of the invention to provide a positioning servo controller in which a requested response characteristic can be easily realized even in the case of adjustment of the disturbance response.
It is a fourth object of the invention to provide a positioning servo controller in which optimum adjustment of the positioning state can be easily conducted.
In order to attain the first object, a positioning servo controller according to an embodiment of a first invention comprises: a position controlling section which amplifies a position deviation between a position command issued from a higher-level unit and a position of a controlled object by a position loop gain, and which outputs the amplified deviation; a speed feedforward section which sets a value that is obtained by adding a first feedforward compensation amount to the value output from the position controlling section, as a speed command, the first feedforward compensation amount being obtained by amplifying a differential value of the position command by a first feedforward gain; a speed controlling section which amplifies a speed deviation between the speed command and a speed of the controlled object by a speed loop gain, and which outputs the amplified deviation; an acceleration feedforward section which sets a value that is obtained by adding a second feedforward compensation amount to the value output from the speed controlling section, as an acceleration command, the second feedforward compensation amount being obtained by amplifying a differential value of the first feedforward compensation amount by a second feedforward gain; an acceleration controlling section which amplifies an acceleration deviation between the acceleration command and an acceleration of the controlled object by an acceleration loop gain, and which outputs the amplified deviation as a torque command; and a torque amplifier which drives the controlled object on the basis of the torque command.
As described above, the positioning servo controller of the embodiment comprises the acceleration controlling section which outputs the value obtained by amplifying the acceleration deviation between the acceleration command and the acceleration of the controlled object by the acceleration loop gain, as the torque command. Even when a physical quantity of the controlled object contained in a coefficient of a transfer function in which the position command is an input and the position response is an output is unknown, therefore, the value of the acceleration loop gain in the coefficient is a denominator of the physical quantity of the controlled object, and an influence of the value of the physical quantity of the controlled object on the position response can be made negligible by setting the value of the acceleration loop gain to an adequate one. Consequently, a satisfactory control response can be obtained by setting the acceleration loop gain to an adequate value.
In order to attain the second object, a positioning servo controller according to an embodiment of a second invention comprises: a position controlling section which amplifies a position deviation between a position command issued from a higher-level unit and a position of a controlled object by a position loop gain, and which outputs the amplified deviation; a first amplifying section which amplifies the value output from the position controlling section by an adjustment gain, and which outputs the amplified value as a speed command; a differentiating section which differentiates the position of the controlled object to obtain a speed of the controlled object; a speed controlling section which amplifies a speed deviation between the speed command and the speed of the controlled object obtained by the differentiating section, by a speed loop gain, and which outputs the amplified deviation; a second amplifying section which amplifies the value output from the speed controlling section by the adjustment gain, and which outputs the amplified value as a torque command; and a torque amplifier which drives the controlled object on the basis of the torque command.
As described above, in the positioning servo controller of the embodiment, when the speed loop gain and the position loop gain are once set to determine the amount of overshoot, only the time direction is changed by the adjustment gain. Therefore, it is possible to easily realize a requested response characteristic.
Another positioning servo controller according to another embodiment comprises: a position controlling section which amplifies a position deviation between a position command issued from a higher-level unit and a position of a controlled object by a position loop gain, and which outputs the amplified deviation; a first amplifying section which amplifies the value output from the position controlling section by an adjustment gain, and which outputs the amplified value as a speed command; a differentiating section which differentiates the position of the controlled object to obtain a speed of the controlled object; an integrating section which integrates a speed deviation between the speed command and the speed of the controlled object that is obtained by the differentiating section, and which outputs a value that is obtained by multiplying an integral value with a speed loop integral gain; a second amplifying section which amplifies the value output from the integrating section by the adjustment gain, and which outputs the amplified value; a speed controlling section which amplifies a value that is obtained by adding the value output from the second amplifying section to a speed deviation between the speed command and the speed of the controlled object obtained by the differentiating section, by a speed loop gain, and which outputs the amplified deviation; a third amplifying section which amplifies the value output from the speed controlling section by the adjustment gain, and which outputs the amplified value as a torque command; and a torque amplifier which drives the controlled object on the basis of the torque command.
In the positioning servo controller, the invention is applied to a positioning servo controller in which the position is controlled by the P (Proportional) control and the speed is controlled by the P-I (Proportional-Integral) control.
A positioning servo controller of a further embodiment comprises: a position controlling section which amplifies a position deviation between a position command issued from a higher-level unit and a position of a controlled object by a position loop gain, and which outputs the amplified deviation; a first amplifying section which amplifies the value output from the position controlling section by an adjustment gain, and which outputs the amplified value as a speed command; a differentiating section which differentiates the position of the controlled object to obtain a speed of the controlled object; an integrating section which integrates a speed deviation between the speed command and the speed of the controlled object that is obtained by the differentiating section, and which outputs a value that is obtained by multiplying an integral value with a speed loop integral gain; a second amplifying section which amplifies the value output from the integrating section by the adjustment gain, and which outputs the amplified value; a speed controlling section which amplifies a deviation between the value output from the second amplifying section and the speed of the controlled object by a speed loop gain, and which outputs the amplified deviation; a third amplifying section which amplifies the value output from the speed controlling section by the adjustment gain, and which outputs the amplified value as a torque command; and a torque amplifier which drives the controlled object on the basis of the torque command.
In the positioning servo controller, the invention is applied to a positioning servo controller in which the position is controlled by the P (Proportional) control and the speed is controlled by the I-P (Integral-Proportional) control.
In order to attain the third object, a positioning servo controller according to an embodiment of a third invention comprises: a position controlling section which amplifies a position deviation between a position command issued from a higher-level unit and a position of a controlled object, by a proportional gain, and which outputs the amplified deviation; a first amplifying section which amplifies the value output from the position controlling section by a value that is obtained by squaring an adjustment gain, and which outputs the amplified value; a differentiating section which differentiates the position deviation between the position command and the controlled object; a speed controlling section which amplifies a value obtained by the differentiating section, by a differential gain, and which outputs the amplified value; a second amplifying section which amplifies the value output from the speed controlling section by the adjustment gain, and which outputs the amplified value; a feedforward controlling section which outputs a value that is obtained by adding a value obtained by amplifying a value obtained by second-order differentiation of the position command, by a first feedforward gain, to a value obtained by amplifying a value obtained by differentiating the position command, by a second feedforward gain and the adjustment gain; and a torque amplifier which sets a value obtained by adding together the values output from the first and second amplifying sections and the feedforward section, as a torque command, and which drives the controlled object on the basis of the torque command.
As described above, according to the third invention, the feedforward controlling section is disposed to set the control system as a two-degree of freedom system, and the gain of the feedforward controlling section and that of the feedback system can be adjusted by the adjustment gain which is one parameter. Therefore, the gain adjustment for determining the requested response characteristic can be simplified.
In another embodiment, in addition to the above configuration, the controller may further comprise: an integrating section which integrates the position deviation between the position command and the position of the controlled object; an integration controlling section which amplifies a value obtained by the integrating section, by an integral gain, and which outputs the amplified value; and a third amplifying section which amplifies the value output from the integration controlling section, by a value that is obtained by cubing the adjustment gain, and which outputs the amplified value.
In a further embodiment, in addition to the above configuration, the controller may further comprise: a second-order differentiating section which performs second-order differentiation on the position deviation between the position command and the controlled object; and an acceleration controlling section which amplifies a value obtained by the second-order differentiating section, by an acceleration gain, and which outputs the amplified value.
In order to attain the fourth object, an embodiment of a fourth invention comprises: a position controlling section which amplifies a position deviation between a position command issued from a higher-level unit and a position of a controlled object, by a position loop gain, and which outputs the amplified deviation; a first amplifying section which amplifies the value output from the position controlling section by an adjustment gain, and which outputs the amplified value; a speed feedforward controlling section which sets a value that is obtained by adding a first feedforward compensation amount to the value output from the first amplifying section, as a speed command, the first feedforward compensation amount being obtained by amplifying a differential value of the position command by a first feedforward gain; a speed controlling section which amplifies a speed deviation between the speed command and a speed of the controlled object by a speed loop gain, and which outputs the amplified deviation; a second amplifying section which amplifies the value output from the speed controlling section by the adjustment gain, and which outputs the amplified value; an acceleration feedforward section which sets a value that is obtained by adding a second feedforward compensation amount to the value output from the second amplifying section, as an acceleration command, the second feedforward compensation amount being obtained by amplifying a differential value of the first feedforward compensation amount by a second feedforward gain; an acceleration controlling section which amplifies an acceleration deviation between the acceleration command and an acceleration of the controlled object by an acceleration loop gain, and which outputs the amplified deviation as a torque command; and a torque amplifier which drives the controlled object on the basis of the torque command, values of the first feedforward gain and the second feedforward gain being values of functions in which a value of the adjustment gain is used as an argument.
In the positioning servo controller of the fourth invention, the values of the first feedforward gain and the second feedforward gain are those of functions in which the adjustment gain is used as an argument, thereby enabling optimization of the positioning state to be conducted simply by adjusting the adjustment gain. Therefore, optimum adjustment of the positioning state can be easily conducted.